Methane gas generator

Abstract

To provide a compact, high-performance methane fermentation apparatus that efficiently ferments a mixture of food waste, human waste and sewage sludge to generate methane.SOLUTION: The compact, high-performance methane fermentation apparatus uses a tank for storing food waste placed above ground to mix the food waste with appropriate amounts of human waste and sewage sludge to ferment the mixture to generate methane.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for carrying out methane fermentation in a city facility by adding amounts of human waste and sewage sludge to food waste. [Background technology]

[0002] Traditionally, most household and general waste in Japan has been incinerated in waste incineration facilities, emitting large amounts of greenhouse gases. In 1992, an international treaty was concluded at the Earth Summit to tackle the issue of preventing the emission of greenhouse gases on a global scale, calling for the prevention of greenhouse gas emissions by fermenting food waste as methane fuel rather than incinerating it, and under national guidance, bio-plants that use food waste have been commercialized, mainly in regional cities. This method requires vast amounts of land and capital, and in small cities within metropolitan areas, it can be difficult to implement due to issues with securing land for equipment and capital issues.

[0003] Conventionally used underground pit-type waste storage tanks are large and expensive, and the waste storage tank in Patent Document 1 is a novel aboveground type, but is complex and not low-cost, as it requires multiple waste diffusion devices inside the tank.

[0004] The membrane separation method of Patent Document 2 is an intermediate treatment method for the digestive liquid remaining in methane fermentation, and is difficult to apply because the membrane is clogged and the concentrated liquid remains after the treatment, making the process complicated.

[0005] [Patent Document 1] Patent Publication 2018-83716, [Patent Document 2] Patent Publication No. 2019-177332, Summary of the Invention [Problem to be solved by the invention]

[0006] Food waste increases from spring to summer, but its contents also vary depending on the region and seasonal fluctuations. Food waste is overwhelmingly more abundant than night soil and sewage sludge, but food waste alone provides little nutrition for the fermentation bacteria, and the fermentation rate slows due to a lack of minerals, so it is appropriate to add an appropriate amount of night soil and sewage sludge to promote fermentation. Municipalities are responsible for waste disposal, and there is a demand for rapid and stable methane fermentation and wastewater treatment of the associated digestion water. [Means for solving the problem]

[0007] In this invention, a garbage storage tank is installed above ground, and the inside of the garbage storage tank is monitored with a security camera attached to the top of the inside to monitor the garbage inside the tank and the occurrence of blocking and bridging between garbage. If necessary, a vibrator attached to the outer plate of the tank is used to vibrate the plate surface to prevent problems such as food waste sticking and bridging between garbage. The amount of food waste that can be stored has been reduced from the conventional 7 days' worth to 1-2 days' worth, making the garbage storage tank smaller.

[0008] Fermentation of a mixture of food waste, human waste, and sewage sludge (hereinafter referred to as the mixture) is superior to fermentation of food waste alone in the following ways: 1. Adding an appropriate amount of the mixture to food waste shortens the methane fermentation time and improves productivity. 2. By thoroughly mechanically mixing the food waste, mixture, and water in a mixing tank and then supplying them to the fermentation tank, the fermentation became stable and the fermentation time was shortened. 3. Methane fermentation residue is dehydrated and dried, and used as boiler fuel. The generated steam is recovered as a heat source for the fermentation tank, preventing the emission of greenhouse gases. Effect of the Invention

[0009] In this invention, the waste storage tank is installed on the ground and multiple crushers are installed on the ground, which makes it possible to significantly reduce the size, and further, water is added to the food waste mixture, which is mechanically mixed in a mixing tank and then fermented in a fermentation tank, enabling short-term fermentation. By reducing the size of the waste storage tank and shortening the methane fermentation time, a small, high-performance methane fermentation device has been invented.

[0010] The residue remaining in the methane fermentation tank can be dehydrated and dried, and then used as fuel for a boiler to heat the methane fermentation tank, thereby contributing to preventing the emission of greenhouse gases. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a flow diagram of a methane gas generator. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The embodiment of the present invention will be described below with reference to Fig. 1. Food waste 5 is collected from homes, food factories, etc. by garbage trucks 2a, -b, -c, and is loaded onto a lift 1 and fed into a garbage storage tank 4a on a platform 3. When a door 4c is opened, an air curtain 4d acts to prevent odors from leaking. An adsorption device 7 combines activated carbon and a blower to adsorb odors and prevent leakage. A surveillance camera 6 monitors the inside of the garbage storage tank 4a, and when garbage 5 adheres to bridges between food waste 5 in the garbage storage tank 4a or to corners of the garbage storage tank 4a, vibrators 8a, 8b are activated to drop the garbage. In addition, negative pressure is created inside the garbage storage tank 4a and the belt conveyors 9a, -b, -c, etc. to prevent odors from leaking.

[0013] Generally, human waste and sewage sludge are less in quantity than food waste and the amount of methane fermentation is also small, but they contain trace elements such as Fe, Co, and Ni necessary for fermentation, which accelerates methane fermentation and is effective for the fermentation of food waste. The upper limit of the addition rate of the mixture to food waste is generally about 5 to 10%, and an appropriate amount is mixed and added.

[0014] A quantity transmitter 19 is attached to the belt conveyor 9d to constantly adjust the optimum amount of human waste and sewage sludge mixed based on the sorted food waste 5. An appropriate amount of water is then added, and the mixture is first thoroughly stirred with the stirring blades 20 of the mixing tank, and then supplied to the methane fermentation tank 26, thereby shortening and stabilizing the fermentation process.

[0015] In this way, when the mixture is added to food waste and artificially fermented into methane, the fermentation period will be longer if the fermentation temperature is selected as medium temperature (35℃) or high temperature (50℃), and the methane production rate will be higher at high temperature than at medium temperature. Furthermore, if the amount of liquid (human waste + sewage sludge) is increased relative to the solid content of the food waste, the methane gas production rate will increase, but the pH will rise and the generation of ammonia nitrogen will increase rapidly.

[0016] Even if the proportion of the mixture added to food waste is increased, the amount of methane generated will be capped at around 10% in Omaka.

[0017] The hydrogen sulfide concentration in the methane gas fermented by this method exceeds 1000 ppm, which is higher than the general concentration of 200 to 800 ppm. Since the atmospheric concentration of hydrogen sulfide is legally set at 10 ppm or less, it is necessary to absorb and detoxify it in the desulfurizer 27 using the following method. Hydrogen sulfide is absorbed in 2-3% sodium carbonate or hydroxide. ; The removal rate is nearly 100%, and it is turned into harmless salt.

[0018] The invention of a small above-ground waste storage tank and a high fermentation rate for methane gas has been commercialized, and the combination of a small, high-performance methane gas fermentation device has made it possible to ferment food waste into methane gas without burning it, even on small sites in small cities.

[0019] The following benefits are achieved by installing a methane gas generator at a sewage plant, etc. (1) Reclaimed water from sewage plants can be used as an absorption liquid for hydrogen sulfide in desulfurizers, etc. (2) When an odor leaks, the concentration of the odor decreases within the sewerage plant. [Industrial Applicability]

[0020] The methane gas generating apparatus of the present invention can recover methane without incinerating food waste in a small space in an urban area where it is difficult to obtain a large new site. [Explanation of symbols]

[0021] Regarding Figure 1 in the attached drawing, TIFF2025016637000002.tif71601 Garbage truck lift 2a Garbage truck (full of garbage) 2b Garbage truck (full of garbage) 2c Garbage truck (when garbage is being put in) 3 Mounting stand 4a Refuse storage tank (main body) 4b Garbage inlet door (closed) 4c. Insertion door (showing garbage being inserted) 4d Air curtain (air jet to prevent odor leakage) 5. Food waste (before sorting) 6. Surveillance Cameras 7 Odor absorber (Combines activated carbon and ventilation fans to prevent odor leakage.) 8a,8b Vibrator 9a,-b,-c,-d Belt conveyor (9d is equipped with a monitor for measuring the weight of food waste.) 10 Temporary garbage storage tank 1 11 Crusher 12 Crusher soundproof cover 13 Intermediate garbage storage tank 2 14 Sorting Machine 15 Sorting machine cover 13 Temporary garbage storage tank 2 14 Sorting Machine 15 Sorting machine cover 16 Food waste (after sorting) 17 Garbage other than food waste (plastics, etc. that are mixed in after sorting) 18 Garbage truck 19 Load cell (transmitter) 20 Mixing tank (with mixing blades inside) 21 Sewage collection vehicle 22 Sewage sludge (supplied through pipes) 23 Human waste and sewage sludge filters 24 Temporary sewage and sludge mixed storage tank 25 Sewage and sludge flow meter 26 Fermentation tank 27 Desulfurizer 28 Methane Gas Tank 29 Methane gas (product) 30 Treated Water 31 Dehydrator (mechanical) 32 Dryer 33 Bagasse

Claims

1. This methane gas generator uses garbage, human waste, and sewage sludge as raw materials, has a rectangular or cylindrical top and a tapered bottom shape to fit the shape of the top, a surveillance camera inside the top of the tank and multiple vibrators on the sides of the tank, a food waste storage tank installed above ground, and multiple mechanically movable conveyor belts, crushers, and sorters, and dehydrates and dries the residue after methane fermentation, carbonizing it and using it as boiler fuel.

2. 2. A methane gas generating apparatus comprising: a mixing tank for mixing the amount of food waste as claimed in claim 1 with an amount of human waste and sewage sludge optimal for methane fermentation; and water; and a mixing tank for mixing the food waste and sewage sludge in an amount optimal for methane fermentation.

3. 3. A methane gas generating device as claimed in claim 1 or 2, characterized in that a plurality of conveyors, crushers and sorters are installed for each category of the petition 1.

4. A methane gas generating apparatus satisfying claims 1, 2 and 3, the installation site of which is adjacent to an existing sewage plant or the like.

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